There can be some negative consequences. What vitamins are you taking?
Excess vitamin C or zinc can give you muscle cramps and diarrhea for example.
The thing with vitamins is that there is no added benefit to cramming high quantities in your diet. Once you've reached your recommended amount, your body stops absorbing them into the bloodstream in the same way.
Also, overdosing on vitamins is almost impossible to do by accident.
Finally, if you're bodybuilding, I believe you should be focusing on your protein intake as this is what builds muscle mass.